Trench (Trench excavation) means a narrow excavation (in relation to its length) made
below the surface of the ground. In general, the depth is greater than the width, but
the width of a trench (measured at the bottom) is not greater than 15 feet.
Cave-ins pose the greatest risk and are much more likely than other excavation-related accidents to result in worker fatalities. Other potential hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. Do not enter an unprotected trench.